Patent Application
20240122861
The present disclosure relates generally to electroresponsive biopolymer capsules that are capable of delivering encapsulated actives. The electroresponsive biopolymer capsules have applications in at least the pharmaceutical, biomedical, and electronic industries.
The background description provided herein gives context for the present disclosure. Work of the presently named inventors, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art.
Soft materials filled with water are widely encountered in biomedical and consumer products. Two classes of such materials are hydrogels electroresponsive biopolymer capsules for delivery of encapsulated actives and capsules. A hydrogel is a water-filled network of polymer chains, with the network being formed by either covalent or physical crosslinks between the chains. A capsule is a spherical structure in which the core is either an aqueous solution or gel whereas the shell is a distinct layer. In some cases, the shell can have the same chemistry as the core but a higher degree of crosslinking. In other cases, the shell can be a coacervate or even a covalently crosslinked layer whereas the core can be physically crosslinked. Both gels and capsules find use in biomedical applications such as drug delivery and tissue engineering, as well as in soft robotics and wearable devices.
A recurring theme has been to make these gels and capsules responsive to external stimuli such as solution pH, salt concentration, temperature, light (at various wavelengths), magnetic fields, and electric fields. Among the stimuli of interest, an emerging one is the electric field, which is particularly attractive because it can be easily turned on and off at a particular location (i.e., with spatial precision) as well as at a precise time (i.e., with temporal precision). Other stimuli such as pH, ionic strength, and temperature cannot achieve the same level of spatial or temporal precision. Light can do so under some cases, but light gets attenuated as it passes through many materials. Moreover, light sources are bulky whereas electric fields can be applied with just a battery (DC) or by connecting to the commercial AC electric supply. In turn, electrical stimuli can be exploited even in portable devices that can be controlled wirelessly and from remote locations, e.g., through the Internet (via Bluetooth).
Electroresponsive soft materials have typically been made using conductive polymers (CPs), such as polypyrroles and polythiophenes, where the charge carriers are electrons. For example, drugs have been chemically conjugated to such CPs, and upon applying an electric current, the release of these drugs from the CPs has been triggered. Alternatively, instead of CPs, electronic conductivity has been imparted to soft materials by adding conductive nanoparticles such as carbon nanotubes (CNTs). For instance, capsules were created with CNTs in their shells and found that the capsules became more permeable under an electric field. However, materials such as CPs and CNT-based composites have their limitations because they are either expensive or difficult to synthesize and are generally not biodegradable or biocompatible. Note also that, for a response to occur in an electronically conductive material, it must be in direct contact with an electrode (i.e., the source of current).
Thus, there exists a need in the art for cost-effective, easy to synthesize electroresponsive biopolymer capsules that are capable of delivering encapsulated actives.
An alternative to electrons is to rely on ions as the charge carriers. Polyelectrolytes, i.e., polymers with ionizable backbones, are widely available and are biocompatible. Hydrogels based on polyelectrolytes have been investigated in electric fields. The hydrogels can be placed in solution either with or without direct contact with the electrodes before applying a current. In some studies, bulk gels have been reported to shrink (or swell) under a field. If such shrinking occurs non-uniformly, the gel can be also made to bend, and this bending can further be transduced into a slithering motion of the gel. Several others have also reported that gel films can be eroded by applying a field (all these films were in contact with one electrode. Such erosion of gel films has been used to deliver drugs entrapped in the films. In addition, electrical response has also been reported for certain nanoscale polymer vesicles (formed by the self-assembly of special block copolymers or homopolymers) by exploiting their sensitivity to redox conditions.
There also exists a need in the art to investigate spherical gels or capsules made from polyelectrolytes and significant transformations to such capsules by electric fields.
Two types of capsules that have been extensively studied by the present inventors are based on the common biopolymers (polysaccharides) Alginate and Chitosan. See e.g.: Lee, et al., “Biopolymer capsules bearing polydiacetylenic vesicles as colorimetric sensors of pH and temperature.” Soft Matter 2011, 7, 3273-3276; Dowling, et al., “Self-destructing ‘mothership’ capsules for timed release of encapsulated contents.” Langmuir 2013, 29, 7993-7998; Ghaffarian, et al., “Chitosan-Alginate microcapsules provide gastric protection and intestinal release of ICAM-1-targeting nanocarriers, enabling GI targeting in vivo.” Adv. Funct. Mater. 2016, 26, 3382-3393; and Lu et al. “A new design for an artificial cell: Polymer microcapsules with addressable inner compartments that can harbor biomolecules, colloids or microbial species.” Chem. Sci. 2017, 8, 6893-6903. Each of the aforementioned publications are hereby incorporated by reference in their entireties herein.
In the case of a gel, it can be induced to swell or shrink in response to the above stimuli. See e.g., Gargava, et al., “Smart hydrogel-based valves inspired by the stomata in plants.” ACS Appl. Mater. Interfaces 2016, 8, 18430-18438. Alternatively, a bulk gel can be actuated to change its shape: for example, a flat sheet can fold into a pancake or tube in response to the same stimuli. See e.g., Athas et al., “Cation-induced folding of alginate-bearing bilayer gels: an unusual example of spontaneous folding along the long axis.” Soft Matter 2018, 14, 2735-2743. In the case of capsules, responses that can be induced include (i) capsule inflation and bursting, see e.g., DeMella et al., “Catalyst-loaded capsules that spontaneously inflate and violently eject their core.” Langmuir 2019, 35, 13718-13726; (ii) autonomous capsule motion, see e.g., Lu et al., “Catalytic propulsion and magnetic steering of soft, patchy microcapsules: Ability to pick-up and drop-off microscale cargo.” ACS Appl. Mater. Interfaces 2016, 8, 15676-15683; (iii) capsule color changes; or (iv) an abrupt change in capsule permeability, see e.g., Zarket et al., “Onion-like multilayered polymer capsules synthesized by a bioinspired inside-out technique.” Nat. Commun. 2017, 8, 193. Each of the aforementioned publications are hereby incorporated by reference in their entireties herein.
The use of electric fields to stimulate the delivery of drugs or other active ingredients is of great interest for wearable electronics and other applications. Most attempts at electrically induced delivery with soft materials in water have focused on electronically conducting polymers (e.g., polypyrroles) or conductive nanocomposites (e.g., polymers with carbon nanotubes). Here, electrical responses are induced even in structures made from nonconducting biopolymers that are widely available, biocompatible, and biodegradable. For example, spherical capsules can be created from the anionic polysaccharide Alginate by crosslinking with cations like Ca2+ or Cu2+. When these capsules are placed in aqueous solution and subjected to a DC electric field of about 8 V/cm, they deform within a couple of minutes and then burst and disintegrate into pieces within about five minutes (5 min). Capsules across a range of length scales such as two hundred micrometers to two centimeters (200 μm to 2 cm) respond in the above manner, and the electroresponse persists even if the capsules are embedded in a nonionic gel matrix. The electroresponse is due to electrophoretic migration of charged species (ions and/or polyelectrolyte chain-segments) within (or out of) the capsules. In an Alginate capsule, the cations are induced to migrate away from the positive electrode, which creates a weakly-crosslinked region of the capsule that swells appreciably. This anisotropic swelling continues until the capsule eventually bursts. Electroresponsive capsules have applications that highlight the spatial and temporal accuracy possible with an electrical stimulus. The bursting of capsules can be used to release solutes loaded inside these structures. Also, even the deformation of intact capsules can be used to create electrically actuatable valves, where a liquid flows out through the valve only when a capsule plug is dislodged. Examples of the present disclosure involve and include electrically induced bursting of aqueous capsules made from biopolymers based on ‘switching on’ the release of payloads.
The following objects, features, advantages, aspects, and/or embodiments, are not exhaustive and do not limit the overall disclosure. No single embodiment need provide each and every object, feature, or advantage. Any of the objects, features, advantages, aspects, and/or embodiments disclosed herein can be integrated with one another, either in full or in part.
It is a primary object, feature, and/or advantage of the present disclosure to improve on or overcome the deficiencies in the art.
It is a further object, feature, and/or advantage of the present disclosure to place soft materials in water and to allow for those soft materials to respond to an electric field. Further efforts are undertaken to determine what types of materials comprise said soft materials. For example, capsules (with liquid or gelled cores) of anionic Alginate and the cationic Chitosan polymers, formed by noncovalent interactions, can be placed in water and a moderate DC electric field (˜10 V/cm) is applied using remote electrodes (i.e., the electrodes do not touch the capsules). The capsules deform or swell anisotropically within a minute and then rapidly burst within about five minutes (5 min), thereby releasing their internal contents.
It is still yet a further object, feature, and/or advantage of the present disclosure to provide biodegradable and/or biocompatible electroresponsive biopolymer capsules. For example, a significant electroresponse is indeed possible in spherical gels and capsules made from common biopolyelectrolytes—including the anionic Alginate and the cationic Chitosan—which are widely used in biomedical applications.
It is still yet a further object, feature, and/or advantage of the present disclosure to determine an optimal size for said capsules. Capsules across a range of length scales: two hundred micrometers to two centimeters (200 μm to 2 cm) can deform or swell anisotropically quickly, thereby releasing their internal contents.
It is still yet a further object, feature, and/or advantage of the present disclosure to tune the electroresponse of the capsules by varying the field strength as well as the capsule composition. A mechanism based on electrophoretic migration of charged species (ions and/or chain-segments) can be employed within or out of the capsules.
It is still yet a further object, feature, and/or advantage of the present disclosure to deliver encapsulated actives without requiring direct contact with an electrode, using the electroresponsive biopolymer capsules. The encapsulated actives that are delivered can include a wide variety of molecular weights, such as small matter with a molecular weight of ˜5000 g/mol, and larger matter with a molecular weight of ˜40,000 g/mol (e.g. proteins). The encapsulated actives can be and/or can be embedded within biologics. The ability to “deliver on demand” several types of encapsulated actives is a great benefit that is not solved by others in the art.
It is still yet a further object, feature, and/or advantage of the present disclosure to provide the ability to shape the soft structures that form the electroresponsive biopolymer capsules. For example, the electroresponsive biopolymer capsules can be spherical prior to be electrically actuated.
It is still yet a further object, feature, and/or advantage of the present disclosure to determine and/or control ideal times for deformation of the electroresponsive biopolymer capsules. Not all of the electroresponsive biopolymer capsules placed in an electrified aqueous solution will break at the same time under identical or even near identical conditions. Rather, it appears that while there is consistency in that the electroresponsive biopolymer capsules will all be destroyed within a small time (e.g., ˜1 min, ˜5 min, ˜10 min, etc.), there will is some variance as to the exact time of when, for example, encapsulated actives would be released from therewithin. Furthermore, it appears (i) the distance from the electroresponsive biopolymer capsules to the electrodes; (ii) the number of electroresponsive biopolymer capsules placed in the aqueous solution; and (iii) the temperature of the aqueous solution and/or electroresponsive biopolymer capsules, have little to no effect as to the time of deformation/rupture. The largest determinant of this time appears to be the composition of the electroresponsive biopolymer capsules, discussed extensively herein.
It is still yet a further object, feature, and/or advantage of the present disclosure to require only a small amount of electrical energy in order to actuate the deformation and/or collapse of the electroresponsive biopolymer capsules. For example, ˜5V is a most preferred power requirement, while ˜10V is a much preferred power requirement, and ˜15V is an acceptable power requirement. This means, as an example, devices employing 3AAA batteries could be used to cause the rupture of said electroresponsive biopolymer capsules. Said devices could even instruct the rupture of said electroresponsive biopolymer capsules in a wireless manner.
The electroresponsive biopolymer capsules disclosed herein can be used in a wide variety of applications. Electrically induced bursting of capsules could be used for the release of encapsulated payloads such as drugs, perfumes, or agrochemicals. Also, the same capsules could be used to create electroactuated valves, which open to allow liquid flow only when an electric field is switched on.
The electroresponsive biopolymer capsules disclosed herein can be incorporated into arrays of valves, other systems, and/or kits which accomplish some or all of the previously stated objectives.
Methods can be practiced which facilitate use, manufacture, synthetization, assembly, maintenance, and repair of electroresponsive biopolymer capsules which accomplish some or all of the previously stated objectives.
According to some aspects of the present disclosure, a system for delivering encapsulated actives comprises an electroresponsive biopolymer capsule that has a cationic component and an anionic component that complements the cationic component and a cell that includes an aqueous solution and a pair of electrodes at least partially submerged in the aqueous solution. Electrolysis of the aqueous solution causes an electrophoretic rearrangement of ions or polyelectrolyte chains in the electroresponsive biopolymer capsule, which deforms the electroresponsive biopolymer capsule. Optionally, the electrodes can comprise graphite slabs. The electrolysis process can be analogized to electrifying an bag that holds a liquid (and the biopolymer).
According to some additional aspects of the present disclosure, the electroresponsive biopolymer capsule comprises a polymer ion capsule. For example, the cationic component can comprise Cu2+ or Ca2+ multivalent cations, the anionic component can comprise an Alginate, and/or the polymer ion capsule can be embedded in an Agarose gel.
According to some additional aspects of the present disclosure, the electroresponsive biopolymer capsule comprises an inner core and an outer shell. The outer shell should be distinct in composition form the core of the inner shell.
According to some additional aspects of the present disclosure, the electroresponsive biopolymer capsule comprises a polymer-surfactant capsule. For example, the cationic component can comprise a Chitosan biopolymer and/or the anionic component can comprise a sodium dodecyl benzene sulfonate (SDBS) surfactant.
According to some additional aspects of the present disclosure, the electroresponsive biopolymer capsule comprises a polymer-polymer capsule. For example, the cationic component can comprise a Chitosan biopolymer and/or the anionic component comprises a nonconducting biopolymer: Gellan gum.
According to some additional aspects of the present disclosure, the electroresponsive biopolymer capsule further comprises carbon black (CB) particles or fluorescent polystyrene latex particles. An inverted optical microscope that detects fluorescence can detect green-fluorescent polystyrene latex (GFPL) nanoparticles and therefore monitor whether the capsules have been ruptured.
According to some additional aspects of the present disclosure, the system further comprises a plurality of electroresponsive biopolymer capsules that are configured to function as a plurality of independently actuatable valves. The plurality of electroresponsive biopolymer capsules may or may not include the aforementioned electroresponsive biopolymer capsule unless otherwise noted.
According to some additional aspects of the present disclosure, the aqueous solution can be a NaCl solution. The aqueous solution can also be water.
According to some other aspects of the present disclosure, an electroresponsive biopolymer capsule comprises a cationic component; an anionic component that complements the cationic component; and an electrophoretic rearrangement of ions or polyelectrolyte chains that when electrically actuated causes the electroresponsive biopolymer capsule to rupture.
According to some other aspects of the present disclosure, a method for delivering encapsulated actives comprising loading an electroresponsive biopolymer capsule with encapsulated actives; and rupturing the electroresponsive biopolymer capsule as a result of a applying a direct current (DC) electric field to an electrophoretic rearrangement of ions or polyelectrolyte chains in the electroresponsive biopolymer capsule, thereby causing the encapsulated actives to be released from the electroresponsive biopolymer capsule.
According to some additional aspects of the present disclosure, the rupturing of the electroresponsive biopolymer capsule occurs regardless of whether there is a change in temperature in the system and/or the rupturing of the electroresponsive biopolymer capsule occurs without directly contacting the capsule.
These and/or other objects, features, advantages, aspects, and/or embodiments will become apparent to those skilled in the art after reviewing the following brief and detailed descriptions of the drawings. The present disclosure encompasses (a) combinations of disclosed aspects and/or embodiments and/or (b) reasonable modifications not shown or described.
Several embodiments in which the present disclosure can be practiced are illustrated and described in detail, wherein like reference characters represent like components throughout the several views. The drawings are presented for exemplary purposes and may not be to scale unless otherwise indicated.
An artisan of ordinary skill in the art need not view, within isolated figure(s), the near infinite distinct combinations of features described in the following detailed description to facilitate an understanding of the present disclosure.
The present disclosure is not to be limited to that described herein. Mechanical, electrical, chemical, procedural, and/or other changes can be made without departing from the spirit and scope of the present disclosure. No features shown or described are essential to permit basic operation of the present disclosure unless otherwise indicated.
Three types of spherical particles made from biopolymers, all of which can be referred to as ‘capsules’, are shown throughout
The first kind of capsule shown in
The second kind of capsule shown in
The third kind of capsule shown in
The capsules 100, 200, 300 in
The above capsules 100, 200, 300 were prepared over a range of sizes, which for simplicity are classified as being in the macroscale (greater than one millimeter in diameter: >1 mm) or the microscale (less than one millimeter in diameter <1 mm). In the case of macroscale capsules, droplet sizes were controlled using plastic pipettes or syringe needles with different gauges. To prepare microscale capsules, the microfluidic setup described in Ghaffarian et al. and Lu et al. (see the preceding citations and incorporations by reference, supra), were used. A key distinguishing feature of this setup is the use of gas as the continuous phase instead of oil. Pulses of compressed air or nitrogen gas are used to shear off aqueous microdroplets from a capillary tip. The microdroplets are then added to a reservoir solution, as before, where they are converted to microcapsules. The microcapsule size is controlled by the feed flow rate and the frequency of gas pulses.
An electric field was applied to the capsules 100, 200, 300 using the rectangular cell 400 shown in
Electrically induced disintegration thus appears to be a widespread effect in capsules assembled by physical interactions. To show the generality of this phenomenon, the above experiments were repeated with multiple capsules in a couple of different ways. First, a number of Alginate-Cu2+ microcapsules 100 were placed in a millimolar (10 mM) NaCl solution 402 and applied the fifteen volts (15 V) field. As shown in
One can estimate the breaking time of a microcapsule, i.e., the time at which a rupture is first detected by optical microscopy. The effects of different variables on this breaking time are discussed as follows. All the experiments were done on Alginate-Cu2+ microcapsules 100. First, the applied voltage was varied.
Next, we varied the parameters influencing the structure of Alginate-Cu2+ capsules 100. These capsules are prepared by dropwise addition of two percent (2%) Alginate 104 into a solution of Cu2+102 (typically 8%). As a liquid drop stays in the Cu2+ solution 102, the liquid drop gets converted into a solid capsule. The time the drop remains in the Cu2+ solution 102 before being washed is the incubation time (typically, this is held at two minutes: 2 min). The longer this time, the higher the density of crosslinks between Alginate chains 104 and Cu2+ ions 102, and thus the stronger the capsule. Also, with a longer incubation time, the crosslinking will be more uniform throughout the droplet, resulting in less variation between the capsule core and shell.
Another variable is the capsule size, which as mentioned above can be varied from the micro to the macroscale.
Alginate capsules 100 can be formed by crosslinking with several multivalent cations 102, and cation type was the next variable we studied. We tested macroscale Alginate capsules 100 formed using Cu2+ (our typical case), as well as calcium (Ca2+), zinc (Zn2+), iron (Fe2+), aluminum (Al3+) and holmium (Ho3+). All capsules were formed by dropping two percent (2%) Alginate 104 into eight percent (8%) solutions of the respective cations 102 and incubating for two minutes (2 min). The breaking time of each capsule under a fifteen volts (15 V) field is plotted in
All the experiments reported thus far have been done with ten millimolar (10 mM) NaCl as the background electrolyte. The breaking of Alginate-Cu2+ capsules 100 in the absence of salt, i.e., in deionized (DI) water, was also examined. In that case, the capsules ruptured when subjected to a voltage of fifteen volts (15 V), but it took longer (greater than fifteen minutes: >15 min) compared to the baseline results. In the absence of salt, the current recorded during the test is very low due to the low ionic conductivity of the solution. One and one hundred millimolar (1 and 100 mM) NaCl was then tried, but there was no significant difference in the breaking time compared to the ten millimolar (10 mM) case. One reason to avoid high NaCl concentrations is because Alginate-Cu2+ capsules 100 slowly disintegrate due to exchange of Cu2+ with Na+ ions. Based on all these findings, we chose to perform all the other tests with capsules in ten millimolar (10 mM) NaCl solutions.
Determining what the mechanism for electrical disintegration of the capsules causes the capsules to break under an electrical stimulus involves an integration of knowledge from polymer physics, electrochemistry, colloid science, and thermodynamics. It is worth mentioning Alginate capsules 100 can ruptured by an electric field even when embedded in an Agarose gel. Agarose is a nonionic biopolymer that forms gels upon cooling a hot sol. Spherical gels of Agarose (macroscale, approximately two millimeter radius: ˜2 mm) can be made by dropping a hot Agarose solution into a cold reservoir. When these gels are tested in a fifteen volts (15 V) field, they remain intact. This implies that the polymer chains in a capsule or gel must be charged (i.e., should be polyelectrolytes) for electrical rupture to be seen. Capsules formed by contacting Chitosan with glutaraldehyde (GA) were also tested. These capsules do not rupture in a fifteen volts (15 V) field. In these capsules, GA forms covalent bonds between amines on adjacent Chitosan chains. Evidently these covalent bonds are too strong to be broken by an electrical stimulus. Thus, the electrical rupture only occurs in capsules formed by weak, physical bonds of an ionic or electrostatic nature.
Given that polyelectrolytes and electrostatic interactions are present in the capsules 100, 200, 300, pH changes are partially responsible for their specific response. pH dovetails with an electrochemical mechanism. That is, when a current passes through the solution at the voltages studied, water gets electrolyzed, and in turn, a pH gradient is generated in the solution. The pH will be lowered at the anode 404+ due to generation of H+ ions near it and conversely, higher at the cathode 404−. When this pH wave reaches the capsule, and taking the case of an Alginate capsule 100, it was expected the left (+) side of the capsule would experience a lower pH than the right (−) side. The low pH was expected to make the left side shrink. However, surprisingly, the opposite is observed where this side swells before breaking. Also, we studied Alginate-Cu2+ capsules 100 in solutions of different pH without an electric field. No changes are seen at high pH, while there was some shrinking of the capsules at low pH. In no case did the capsules break simply due to pH. The distance to the electrode(s) also did not influence capsule breakage (
The effects of ionic strength and osmotic effects were also considered. As noted earlier, Alginate-Cu2+ capsules 100 show electrical rupture regardless of the salt (NaCl) concentration. For comparison, in the absence of the field, if an Alginate capsule 100 is placed in a concentrated (>100 mM) salt solution, the capsule will shrink within a few minutes. If placed back in DI water, the capsule will swell back to its original size. This swelling and shrinking are due to differences in osmotic pressure (i.e., the total concentration of ions and molecular species) between the capsule lumen and the external solution. But these osmotic gradients seem to be insufficient to break the capsules. Overall, if electrical rupture was solely related to osmotic pressure or ionic strength, one would need to explain why these quantities would change sharply upon applying the field. As such, these possibilities can be ruled out as well.
The mechanism for the electrical rupture of the capsules 100, 200, 300 is observed in
Some cations 102 might escape out of the capsule 100 under an electric field, and this can be tested experimentally. For this, Alginate-Ca2+ capsules 100 and eriochrome black T (EBT), a well-known colorimetric indicator for Ca2+. An ammonia-buffered solution of EBT is blue, but as Ca2+ is added, the solution turns from blue to violet to red (
The same mechanism for electrical rupture also applies to Chitosan-SDBS capsules 200 and Gellan-Chitosan capsules 300. In those cases too, the electric field will exert forces in opposite directions on the cationic and anionic species in the capsules. In Chitosan-SDBS capsules 200, the SDBS surfactants 208 are relatively small and comparable to the cations in Alginate capsules 100. In Gellan-Chitosan capsules 300, both the constituents are polymers, but they are expected to be confined to a thin shell. Both these capsules 200, 300 have a liquid core whereas Alginate capsules 100 have a gelled core (
Electrical disintegration can be used to release payloads encapsulated in the capsules such as therapeutics or agrochemicals. Examples of such payload release have been shown in
We extended this electro-actuated valve design to incorporate three valves (
Materials. Most of the chemicals described above were purchased from Sigma-Aldrich. This included three biopolymers: Alginate (medium viscosity alginic acid, sodium salt from brown algae), Chitosan (medium molecular weight), and Agarose (type I-A, low EEO); and the salts: copper chloride (CuCl2·2H2O), calcium chloride (CaCl2·2H2O), aluminum sulfate (Al2(SO4)3·xH2O), zinc sulfate (ZnCl2·7H2O), holmium chloride (HoCl3·7H2O), and sodium tripolyphosphate (TPP). Other chemicals included sodium hydroxide (NaOH, in pellet form), glutaraldehyde (GA, 50% in water), and the dyes Eriochrome Black T (EBT), Rhodamine B (RB) and Rhodamine 6G (R6G). Iron chloride (FeCl3, anhydrous) was purchased from Acros Organics, acetic acid (CH3COOH, glacial) from Fisher Scientific, sodium chloride (NaCl) from EMD Millipore, hydrochloric acid (HCl) from BDH, and ammonium hydroxide from J. T. Baker. The surfactant sodium dodecylbenzenesulfonate (SDBS, hard type) was from TCI America, while the biopolymer Gellan gum 308 (Kelcogel F) was from CP Kelco. Graphite sheets (3 mm thickness) were from Saturn Industries. Carbon black (CB) nanoparticles (N110) were from Sid Richardson Carbon Company. Green-fluorescent polystyrene latex (GFPL) nanospheres (diameter ˜100 nm) were from Polysciences. Deionized (DI) water was used to prepare aqueous solutions.
Macrocapsule Synthesis. To prepare Alginate capsules 100, a feed solution of two percent (2%) of Alginate 104 in deionized (DI) water was dropped into a reservoir solution containing multivalent cations 102, with a typical solution being eight percent (8%) CuCl2 102. The incubation time in the reservoir was typically two minutes (2 min). After this time, the capsules were removed, washed with DI water, and stored in a ten millimolar (10 mM) NaCl solution or in DI water. To prepare Chitosan capsules 200, 300, a feed of two percent (2%) Chitosan 206 in 0.2 M acetic acid was dropped into a reservoir solution of five percent (5%) SDBS 208, where it was incubated for three to five minutes (3 to 5 min), then washed and stored as above. To prepare Gellan-Chitosan capsules 300, a feed of one percent (1%) Gellan gum 308 in DI water was dropped into a reservoir of 1% Chitosan 306 in acetic acid. After a three minutes (3 min) incubation, the capsules were washed and stored as above. In all the above cases, the size of the capsules was dictated by the size of the feed droplet, which was varied by using either plastic transfer pipettes or syringe needles of different gauges. A typical radius of each of the above macrocapsules was two centimeters (2 cm). To make capsules containing particles, one quarter percent to one half percent (0.25 to 0.5%) CB or one tenth percent (0.1%) of GFPL were added to the biopolymer feed solution. This was then sonicated using a tip sonicator for one minute (1 min) to disperse the particles prior to its use for capsule synthesis.
In addition to the above capsules, all of which are electroresponsive (
Microcapsule Synthesis. Microcapsules (sizes <1 mm) were prepared using a microfluidic method developed by our group that has been described in detail previously. The feed and reservoir solutions for each type of capsule were identical to those mentioned above. The feed flow was controlled by a syringe pump and the feed was sent through a glass capillary tube with an inner diameter typically of 200 μm. Compressed nitrogen gas was sent as a sheath around the capillary. A gas-flow controller was connected to a function generator (BK Precision) to generate gas pulses, with the gas pressure set at fourteen pounds per square inch (14 psi). Details of the setup, together with photos, are provided in the SI section of our earlier paper. For every pulse of gas, an aqueous droplet was dislodged from the tip of the capillary. The flow rate of the liquid as well as the frequency of the pulsing gas dictated the volume of the liquid droplet. Droplets generated this way were very uniform, with polydispersities of <3% in their size. Upon incubation in the reservoir solution, the droplets were converted to microcapsules. Thereafter, they were filtered out, washed with DI water and stored in a ten millimolar (10 mM) NaCl solution.
Electrical Rupture Tests.
Optical and Fluorescence Microscopy. Brightfield images of the microcapsules under the field were obtained using an inverted optical microscope 500 (Zeiss Axiovert 135 TV) using a two and a half times (2.5×) objective. Fluorescence images of capsules containing GFPL particles were taken using a band pass excitation filter (450-490 nm) and a band pass emission filter (515-565 nm). All images were analyzed using ImageJ software.
Ca2+-EBT Colorimetry. The EBT solution was made by dissolving 0.005 g EBT in twenty grams (20 g) DI water. The ammonia buffer was prepared by mixing two milliliters (2 mL) of twenty nine percent (29%) ammonium hydroxide, one milliliter (1 mL) of concentrated HCl, and two milliliter (2 mL) of DI water. Alginate-Ca2+ macrocapsules were made as described above with their incubation time extended to twenty four hours (24 h) so that they did not break in the field. For each experiment, five (5) capsules were placed in the test cell 400 along with two milliliters (2 mL) of ten millimolars (10 mM) NaCl (see schematic in
Statistics. Values of the capsule breaking time shown in
From the foregoing, it can be seen that the present disclosure accomplishes at least all of the stated objectives.
The following table of reference characters and descriptors are not exhaustive, nor limiting, and include reasonable equivalents. If possible, elements identified by a reference character below and/or those elements which are near ubiquitous within the art can replace or supplement any element identified by another reference character.
Unless defined otherwise, all technical and scientific terms used above have the same meaning as commonly understood by one of ordinary skill in the art to which embodiments of the present disclosure pertain.
The terms “a,” “an,” and “the” include both singular and plural referents.
The term “or” is synonymous with “and/or” and means any one member or combination of members of a particular list.
As used herein, the term “exemplary” refers to an example, an instance, or an illustration, and does not indicate a most preferred embodiment unless otherwise stated.
The term “about” as used herein refers to slight variations in numerical quantities with respect to any quantifiable variable. Inadvertent error can occur, for example, through use of typical measuring techniques or equipment or from differences in the manufacture, source, or purity of components.
The term “weight percent,” “wt-%,” “percent by weight,” “% by weight,” and variations thereof, as used herein, refer to the concentration of a substance as the weight of that substance divided by the total weight of the composition and multiplied by 100. It is understood that, as used here, “percent,” “%,” and the like are intended to be synonymous with “weight percent,” “wt-%,” etc.
The term “substantially” refers to a great or significant extent. “Substantially” can thus refer to a plurality, majority, and/or a supermajority of said quantifiable variables, given proper context.
The term “generally” encompasses both “about” and “substantially.”
The term “configured” describes structure capable of performing a task or adopting a particular configuration. The term “configured” can be used interchangeably with other similar phrases, such as constructed, arranged, adapted, manufactured, and the like.
Terms characterizing sequential order, a position, and/or an orientation are not limiting and are only referenced according to the views presented.
A “biopolymer” is a natural polymer produced by cells of living organisms.
Biopolymers can comprise monomeric units that are covalently bonded in chains to form larger molecules. Example biopolymers include polynucleotides, polypeptides, and polysaccharides. RNA and DNA are long polymers of nucleotides. Polypeptides include proteins and shorter polymers of amino acids; some major examples include collagen, actin, and fibrin. Polysaccharides are linear or branched chains of sugar carbohydrates; examples include starch, cellulose, and Alginate. Other examples of biopolymers include natural rubbers (polymers of isoprene), suberin and lignin (complex polyphenolic polymers), cutin and cutan (complex polymers of long-chain fatty acids), melanin, and polyhydroxyalkanoates (PHAs).
A “polypyrrole” (“PPy”) is an organic polymer obtained by oxidative polymerization of pyrrole. It is a solid with the formula H(C4H2NH)nH. It is an intrinsically conducting polymer, used in electronics, optical, biological and medical fields.
A “nanocomposite” is a multiphase solid material where one of the phases has one, two or three dimensions of less than one hundred nanometers (100 nm) or structures having nanoscale repeat distances between the different phases that make up the material.
Biological products include a wide range of products such as vaccines, blood and blood components, allergenics, somatic cells, gene therapy, tissues, and recombinant therapeutic proteins. “Biologics” can be composed of sugars, proteins, or nucleic acids or complex combinations of these substances, or may be living entities such as cells and tissues. Biologics are isolated from a variety of natural sources—human, animal, or microorganism—and may be produced by biotechnology methods and other cutting-edge technologies. Gene-based and cellular biologics, for example, often are at the forefront of biomedical research, and may be used to treat a variety of medical conditions for which no other treatments are available.
The “invention” is not intended to refer to any single embodiment of the particular invention but encompass all possible embodiments as described in the specification and the claims. The “scope” of the present disclosure is defined by the appended claims, along with the full scope of equivalents to which such claims are entitled. The scope of the disclosure is further qualified as including any possible modification to any of the aspects and/or embodiments disclosed herein which would result in other embodiments, combinations, subcombinations, or the like that would be obvious to those skilled in the art.
This application claims priority under 35 U.S.C. § 119 to provisional patent application U.S. Ser. No. 63/380,002, filed Oct. 18, 2022. The provisional patent application is herein incorporated by reference in its entirety, including without limitation, the specification, claims, and abstract, as well as any figures, tables, appendices, or drawings thereof.
This invention was made with government support under W911NF1820170 awarded by the Department of the Army, Army Research Office. The government has certain rights in the invention.
| Number | Date | Country | |
|---|---|---|---|
| 63380002 | Oct 2022 | US |
